Geophysical Information Research Articles

Shear wave velocity structure at the Fukushima forearc region based on H/V analysis of ambient noise recordings by ocean bottom seismometers

SUMMARYThis study presents the shear wave velocity (VS) structures of sedimentary sequences and a section of the upper crustal layer in the Fukushima forearc region of the Japan Trench subduction zone, which were obtained by analysing the horizontal-to-vertical (H/V) spectral ratios of ambient vibration records. The H/V curves were derived using 31 d of continuous seismic data from 3 broad-band and 16 short-period ocean bottom seismometer (OBS) stations. Using the broad-band data, H/V ratios from 0.01 to 10 Hz were derived, but the ratios below 0.1 Hz frequencies were unusually large and temporally unstable. Characterization of seismic noise energy from ∼1 yr of seismic data of three broad-band OBSs revealed variable and elevated energy conditions below 0.1 Hz due to typical long-period oceanic noise; we link these observations with the unstable H/V ratios below this frequency. Therefore, H/V analysis was performed in the frequency range of 0.1–10 Hz for both broad-band and short-period OBSs to obtain subsurface VS profiles. For the forward calculation of the H/V ratios in the inversion process, we used the recently developed ‘hvgeneralized’ method, which is based on the diffuse field assumption, and accounts for the water layer on top of stratified media. Moreover, available prior geological and geophysical information was utilized during the inversion of the H/V curves. We found that subsurface VS ranged from approximately 30 m s−1 at the seabed to approximately 4900 m s−1 at 7000 m below the sea floor (mbsf). Starting with the best model candidate at each OBS location, the effect of the water layer on the H/V curve in the deep ocean was investigated by comparing synthetic H/V curves with and without the water layer. The synthetic H/V analysis revealed that the water layer had a significant effect on H/V amplitudes at higher frequencies (>1 Hz), whereas comparatively little effect was observed at lower frequencies (<1 Hz). This study provides an empirical basis for H/V analysis using OBS data to determine VS down to several kilometres of sedimentary sequences to the upper crust with high-resolution.

Using a non-invasive multiple-method approach to characterize rock glaciers in the periglacial critical zone: An example from the San Juan Mountains, Colorado

Anthropogenic climate change threatens water storage and supply in the periglacial critical zone. Rock glaciers are widely distributed alpine aquifers with slower response to temperature increases, that provide the summer water flow of many alpine streams. Knowing the extent and makeup of rock glaciers is necessary to evaluate their potential for water supply. We used non-invasive methods, integrating geological, geomorphological, meteorological, and geophysical information to characterize the internal structure and hydrology of the Upper Camp Bird rock glacier (UCBRG) located on level 3 of Camp Bird Mine in Ouray, Colorado, and assessed the applicability of two electromagnetic induction systems in this highly heterogeneous landform with a history of anthropogenic activity. The time-domain (G-TEM™) system achieved deep subsurface penetration (~100 m) and realistic modeling of the internal structure of the UCBRG: a shell of volcanic rock fragments (<3 m thick; 1–100 Ohm-m), a meltwater component (102–103 Ohm-m), located between 50 and 100 m near the toe (subpermafrost flow), and 1–30 m in the soundings farthest from the toe (suprapermafrost flow within the active layer), and a frozen component (permafrost 50–80 m thick; 103–106 Ohm-m). The frequency-domain system, however, was highly susceptible to local environmental conditions, including anthropogenic objects (i.e., mine carts, lamp posts, tunnel tracks, etc.) and was unable to resolve UCBRG's internal makeup. The non-invasive methodology and general conceptual framework presented here can be used to characterize other alpine aquifers, contributing to the quantification of global water resources, and highlighting the importance of preserving rock glaciers as storage for critical water supply in the future.

Modeling the transition zone of the Cenomanian gas reservoir

Low-pressure gas production is one of the most important tasks in gas field development. To estimate the reserves of previously uninvolved reservoirs with low reservoir properties, it is necessary to analyze available geological and geophysical information for the subsequent creation of a three-dimensional geological model. Based on this model, a filtration model will be built, which allow calculating the flow rates of both actually drilled and designed wells for the entire development period. The model is built on the basis of small amount of information content, but the modeling results sufficiently reflect the presence of a zone of poorly saturated part of the Cenomanian gas reservoir, and structural and petrophysical features of the reservoir in the territory. As a result of the conducted research, the low pressure gas reserves at the Yamburgskoye field were calculated. The calculations, which are given in the article, are correct and don't contradict the Regulations on the creation of permanent geological and technological models of oil and gas and oil fields (RD 153-39.0-047-00).

Испытание пластов на кабеле как метод оперативного уточнения геологогеофизических моделей и оценки запасов углеводородов на этапе геологоразведочных работ

The paper considers benefits of Wireline Formation Testing (WFT) enhanced applications to increase the field geophysical survey methods information content by using advanced pressure survey, downhole fluid analyses with sampling and interval testing including the assessment of reservoir hydrodynamic parameters (permeability, productivity, skin factor, etc.). The results present a comprehensive analysis of well logging data augmented withWFT to determine fluid level contacts and reservoirs saturation in the Lower Cretaceous deposits for a well drilled on Caspian Sea shelf. It was shown the possibility to identify potentially productive gas-saturated intervals by using well logging and WFT in conditions of reduced porosity and permeability properties. Discussed approach is also presented the way how to optimize well testing program through productivity evaluation using the WFT methods in orderto reduce the time for conducting hydrodynamic studies without loss of information content.

Regional Intrusive Signature from the Cameroon Coastal Basins to Bioko Island in Equatorial Guinea (Gulf of Guinea) Using Gravity Studies

The Gulf of Guinea constitutes an area of great petroleum potential yet with very limited geophysical research information. Consequently in this study, a Bouguer anomaly map has been computed from gravity data covering regions stretching from the Cameroon coastal basins to Bioko island (formerly Fernando Po) which is part of Equatorial Guinea. The data were further processed for Source Edge Detection (SED), Euler 3D deconvolution, 3D surface oriented models and 3D voxel solutions. The results confirmed the presence of previously identified intrusive bodies around the Douala and Kribi/Campo sedimentary sub-basins and went ahead to suggest a probable continuity between these two. A possible extension of this body offshore the Gulf of Guinea right up to Bioko island with very striking similarities was also highlighted and it shows characteristic variations in the depth to the surface of the body at different locations.

Применение RGB-синтеза для комплексной интерпретации данных геофизических методов при изучении территорий, загрязненных нефтепродуктами

The information on geological structure as well as on the degree of contamination and geometrical parameters of a pollutant in oil-contaminated areas is necessary for risk assessment, planning of oil products recovery and territory remediation. Geophysical methods are actively used for solving such problems. The work considers the site on the Volga River bank, where soils are contaminated with petroleum products. The aim of the work is to delineate the distribution area of petroleum products. In order to achieve the goal, the set of near-surface geophysical methods (vertical electric sounding, seismic survey) and gas geochemistry were implemented. The results of a new approach to characterization of contaminated sites by RGB-data synthesis have been demonstrated as one of the ways of data interpretation. The method is based on the generalization of the available materials by optically mixing of the data of three spatially distributed characteristics presented in the form of three channels – red, green, and blue – for the purpose of localizing the lenses of gravity-mobile and immobilized oil products. According to the results of the qualitative interpretation of geophysical information, the authors have built a scheme with the proposed contour of oil products distribution in the studied territory. The proposed method can be used for the delineation of oil spills along with the sufficient information obtained by geophysical or other methods (at least three) at the stage of determining the spread of contamination for the sites. This approach can speed up the interpretation process, as such maps overlaying sets the color distribution of different petrophysical characteristics of the soils for the selected depth level, and also eases the task of determination of coordinates when correlating various anomalies, identified by different methods.

Структурное районирование Африкано-Антарктического сектора Южного океана на основе анализа аномальных гравитационного и магнитного полей

The African-Antarctic sector of the Southern Ocean is the least studied part of the World Ocean, the structure and evolution of the tectonosphere of which remains debatable. The complex history of the development of the region under study, accompanied by manifestations of intense magmatic and tectonic activity, has contributed to the formation of a number of large underwater ridges and rises. Identifying the features of the deep structure of the tectonosphere on the basis of the analysis of geophysical information and understanding the geodynamic nature of the morphostructures of the studied region is an urgent problem of marine geophysics and geodynamics. Structural analysis of the anomalous gravitational and magnetic fields of the studied region was carried out. Zoning scheme by the anomalous fields as well as a generalized scheme are constructed. The results of the sestudiesmadeit possible to identify heterogeneous blocks of the lithosphere, which for medon different spreading ridges and are separated by submarine rises.

Effects of Fractures on Buildings and Road Construction: A Case Study of Area BZ, Ahmadu Bello University, Zaria, Nigeria

Structural collapse due to the absence of geophysical information has become a major concern in the construction and building industries today. In this research, we reported the effect of fracture on some selected buildings in Area BZ, Ahmadu Bello University, Zaria. Reflex W software was used to analyze the vertical and horizontal profiles of the subsurface features in two-dimensional (2D) tomography of seismically related regions. The data were collected using MK6 Terraloc seismograph. Seismic refraction method was used to obtain relevant information about the subsurface strata. The velocities of different layers were obtained from the distance-time graph to generate the tomography of the four profiles of 115 m distance each. Results revealed that there are fractures beneath the surface, starting from the depth of 10 m into the basement region as evident in the four (4) profiles with variations in the seismic velocities of 1652 to 2086 m/s and 2521 to 2955 m/s for given strata. The 2D tomography of the study area also revealed that the eastern parts of profiles 1-3 may not be safe for the erection of buildings and other structures without excavation, while profile 4 revealed high levels of structural deformation and it is recommended as a high-risk region that will not support engineering structure. We, however, recommend that further geophysical surveys should be carried out in the area, using Electrical Resistivity Tomography (ERT).

The use of INTEGRO GIS in the integrated geophysical study&#x0D; of the deep structure of oil and gas prospective regions (part 1)

Using the materials of integrated geophysical studies of the Yenisei-Khatanga trough as an example, the methodological outline and techniques for constructing deep physical-geological models (PGM) of large regions using the INTEGRO GIS complex are demonstrated. The presented graph is based on spatial analysis of potential field data, as well as analysis of seismic and geoelectric sections along the lines of integrated profiles of CDP-2D and MTS with the involvement of geological data, borehole data and materials on the physical properties of rock complexes. The results of the analysis are then used to construct the PGM according to the data of individual methods. The research focuses on the construction of a volumetric density model of the region that integrates all geological and geophysical information and is intended to serve as the background for the development/correction of structural-tectonic and evolutionary models of oil and gas bearing region for predictive purposes. The actual results of such constructions for the Yenisei-Khatanga trough region and their significance for oil and gas exploration are discussed.

Reference object on the continent – step on the Arctic shelf

Problem statement. To study the Arctic shelf of the Russian Federation, it is necessary to identify a reference object on the continent, similar in geological structure and sufficiently well studied for forecasting and reasonable assessment of oil and gas bearing objects. Research objectives and tasks are to develop recommendations, based on the data on the reference object, that reduce geological risks during geological exploration both in new promising areas and in areas with confirmed oil and gas potential on the RF Arctic shelf. Methods of research include analysis of geological and geophysical information, lithochemical, X-ray diffraction, electron microscopic studies of mineral paragenesis and variations in the composition of oil and gas bearing strata Results. Based on the analysis of the history of the geological development of the West Siberian Plate and its continuation in the Kara Sea shelf on the continent, a reference object was identified – the North Tazovskaya depression – a structure of the second order of the Bolshekhetskaya megasyneclise. Rock complexes and productive horizons transformation signs have been established based on the study of the North-Tazovskaya depression fluid-active area zoning. The presence of established lithogeochemical, mineral and other parameters of the productive horizon makes it possible to predict reservoir rocks or fluid seals, the distribution of which depends on the degree of secondary changes in predominantly layered silicates, which are indicators of fluid dynamic systems with certain thermobarogeochemical parameters. Scope of results. The North-Tazov basin objects study allows to consider this region as a reference object for the Kara Sea shelf. The study of the reference object oil and gas content requires an integrated approach, which, in addition to geophysical methods, also includes methods for studying hydrothermal-metasomatic transformations of rocks and minerals, which will make it possible to carry out geological exploration work more efficiently in the hard-to-reach conditions of the Arctic shelf

Tectonostratigraphy and history of geological development of North Caspian fold-thrust zone

The presented article is devoted to the actual problem of regional geology — the reconstruction of the history of geological development of the Upper Paleozoic-Triassic complex in the southern part of the North Caspian. Understanding of evolution is one of the necessary conditions for improving the reliability of predicting the geological objects characteristics, the structure of which determines the possibilities for the formation of hydrocarbon accumulations. Despite the rather limited data presented mainly by 2D seismic, the authors created a tectonostratigraphic model of the region. It is based on the results of integrated interpretation of geological and geophysical information, carried out using modern methodological approaches.

Predicting Geotechnical Parameters from Seismic Wave Velocity Using Artificial Neural Networks

Geotechnical investigation plays an indispensable role in site characterization and provides necessary data for various construction projects. However, geotechnical measurements are time-consuming, point-based, and invasive. Non-destructive geophysical measurements (seismic wave velocity) can complement geotechnical measurements to save project money and time. However, correlations between geotechnical and seismic wave velocity are crucial in order to maximize the benefit of geophysical information. In this work, artificial neural networks (ANNs) models are developed to forecast geotechnical parameters from seismic wave velocity. Specifically, published seismic wave velocity, liquid limit, plastic limit, water content, and dry density from field and laboratory measurements are used to develop ANN models. Due to the small number of data, models are developed with and without the validation step in order to use more data for training. The results indicate that the performance of the models is improved by using more data for training. For example, predicting seismic wave velocity using more data for training improves the R2 value from 0.50 to 0.78 and reduces the ASE from 0.0174 to 0.0075, and MARE from 30.75 to 18.53. The benefit of adding velocity as an input parameter for predicting water content and dry density is assessed by comparing models with and without velocity. Models incorporating the velocity information show better predictability in most cases. For example, predicting water content using field data including the velocity improves the R2 from 0.75 to 0.85 and reduces the ASE from 0.0087 to 0.0051, and MARE from 10.68 to 7.78. A comparison indicates that ANN models outperformed multilinear regression models. For example, predicting seismic wave velocity using field plus lab data has an ANN derived R2 value that is 81.39% higher than regression model.

Using Deep Learning to Model Elevation Differences between Radar and Laser Altimetry

Satellite and airborne observations of surface elevation are critical in understanding climatic and glaciological processes and quantifying their impact on changes in ice masses and sea level contribution. With the growing number of dedicated airborne campaigns and experimental and operational satellite missions, the science community has access to unprecedented and ever-increasing data. Combining elevation datasets allows potentially greater spatial-temporal coverage and improved accuracy; however, combining data from different sensor types and acquisition modes is difficult by differences in intrinsic sensor properties and processing methods. This study focuses on the combination of elevation measurements derived from ICESat-2 and Operation IceBridge LIDAR instruments and from CryoSat-2’s novel interferometric radar altimeter over Greenland. We develop a deep neural network based on sub-waveform information from CryoSat-2, elevation differences between radar and LIDAR, and additional inputs representing local geophysical information. A time series of maps are created showing observed LIDAR-radar differences and neural network model predictions. Mean LIDAR vs. interferometric radar adjustments and the broad spatial and temporal trends thereof are recreated by the neural network. The neural network also predicts radar-LIDAR differences with respect to waveform parameters better than a simple linear model; however, point level adjustments and the magnitudes of the spatial and temporal trends are underestimated.

Recent Advances in Modelling Geodetic Time Series and Applications for Earth Science and Environmental Monitoring

Geodesy is the science of accurately measuring the topography of the earth (geometric shape and size), its orientation in space, and its gravity field. With the advances in our knowledge and technology, this scientific field has extended to the understanding of geodynamical phenomena such as crustal motion, tides, and polar motion. This Special Issue is dedicated to the recent advances in modelling geodetic time series recorded using various instruments. Due to the stochastic noise properties inherent in each of the time series, careful modelling is necessary in order to extract accurate geophysical information with realistic associated uncertainties (statistically sufficient). The analyzed data have been recorded with various space missions or ground-based instruments. It is impossible to be comprehensive in the vast and dynamic field that is Geodesy, particularly so-called “Environmental Geodesy”, which intends to understand the Earth’s geodynamics by monitoring any changes in our environment. This field has gained much attention in the past two decades due to the need by the international community to understand how climate change modifies our environment. Therefore, this Special Issue collects some articles which emphasize the recent development of specific algorithms or methodologies to study particular natural phenomena related to the geodynamics of the earth’s crust and climate change.

To the issue of forecasting the main parameters of carbons’ quality based on the vector simulation

During the prospecting the quality parameters, except for ash content, are specified by core samples and laboratory methods (geological sampling). Nevertheless, while prospecting the receipt of the representative sample with all its specified parameters being identical to the parameters of the carbon layer is difficult because of partial core recovery, its choking, etc. So, it is highly necessary to specify and to forecast the parameters of carbons’ quality by “indirect” methods which depend on sample representativeness. According to the experience that we have in specifying ash content by the data of the geophysical bore-hole logging (GBL), it is the geophysical sampling that meets this requirement. However, the deterrent of the use of the GBL data for specifying and forecasting of carbons’ quality parameters is the necessity of taking into consideration of a great number of factors (genetic and epigenetic ones) which can not be analyzed using the current mathematical methods. Only the vector simulation solved this task and helped to use the results of geophysical bore-hole logging for forecasting the parameters of carbons’ quality in full measure. The vector simulation will allow to enhance reliability and informativity while forecasting the main parameters of carbons’ quality in the rock mass according to the GBL data at the stage of geological exploration. While systematizing the geological and geophysical information the developed mathematical model, presented by structural vectors of system’s transient states, will enable to take into account some genetic and epigenetic factors in total. These factors influence the reliability of forecasting about such main parameters of the carbons’ quality as ash state, yield of volatile matters, moisture of analysis sample, thickness of plastic layer in the layers where geological sampling is not conditioning.

Lithology identification using principal component analysis and particle swarm optimization fuzzy decision tree

Lithology identification using geophysical log information is vital for log interpretation and reservoir evaluation. As a result of the highly similar features for log curves that characterize complex lithology, there is significant information redundancy regarding the process of lithology identification. In addition, as a result of the highly nonlinear characteristics of log curves, the mapping relationship with lithology has certain ambiguities and uncertainties, which affect the lithology prediction results. Combining principal component analysis (PCA) and the fuzzy decision tree (FDT) model, we propose a new intelligent lithology identification method that is capable of effectively solving these problems well. However, because of the inaccuracy for empirically set parameters, an adaptive fuzzy decision tree algorithm based on particle swarm optimization (PSO-FDT) was proposed after analyzing the main features of the fuzzy decision tree and using an improved particle swarm optimization (PSO) algorithm to determine the relevant parameters. Compared with the FDT algorithm which determines parameter values empirically, the performance of the PSO-FDT has been significantly improved. Finally, the proposed PSO-FDT model was verified using test data. Experiments confirm that the proposed model is more effective than other lithology identification models. The identification accuracy for all lithologies was equal to or greater than that of the other methods. In addition, the overall accuracy was improved by at least 9.71%.

Cross-validation of time-depth conversion and evaluation of different approaches in the Mesopotamian Basin, Iraq

The time-depth conversion process is a significant task in seismic interpretation to establish the link between geophysical information in the time domain and geological information in the depth domain at/away from well locations. Selecting the suitable velocity model for time-depth conversion to generate an accurate depth map is difficult if the accuracy of these models is unknown. In the current study, the cross-validation technique is used as a tool to diagnose and evaluate the performance of time-depth conversion at/away from well controls to predict the depth of Top Hartha and Zubair reservoirs using the dataset of East Baghdad Oil Field. To test this technique, four common velocity model approaches used for time-depth conversion with different scenarios of velocity parameters (initial velocity V 0 and depth gradient (K)) were applied to produce ten velocity models (1–10). According to the gradient variation of velocity with depth, check shot analysis, the velocity models (1–10) include three key velocities layer-cakes: Layer 1 (Middle Miocene-Upper Cretaceous), Layer 2 (Upper Cretaceous), and Layer 3 (Lower Cretaceous) with 18 horizons from Middle Miocene down to Lower Cretaceous. The cross-validation analysis reveals that the velocity model with a variable surface initial velocity and constant depth gradient (Model 9) was the most accurate with fewer mistie between actual and predicted depth. Consequently, this model is used to construct the depth map of the Hartha and Zubair reservoirs. Finally, this study progresses a workflow that can be applied to the region with any geological setting to investigate time-depth conversion uncertainty.

Разработка ультразвукового приемопередатчика для скважинной телеметрии

Hydrocarbons are the significant part of the Russian Federation's exports. Due the exploration of hard-to-recover reserves, it is necessary to design and improve technical tools and methods to increase the efficiency of the geophysical information transfer in the logging of wells. A new communication channel for the telemetry transfer is proposed and investigated. The main idea is to use an acoustic signal in the ultrasonic frequency band and inner tube space as a transmission media. The inner tube space contains a more homogeneous media than the rocks behind the casing string. The use of ultrasonic frequencies reduces the signal scattering into the annular space. It is assumed that it will improve the reliability of the transferred information. The designed ultrasonic receiver and digital signal transmitter in the “Manchester II” code are presented based on the ma40s4s ultrasonic radiating element and the ma40s4r ultrasonic sensor. A test bench has been designed to evaluate the effectiveness of the technical solution. During the experiments, a significant influence of interference was revealed. Despite significant attenuation in a conductive media, this phenomenon significantly increases the signal amplitude, but makes it difficult to identify it, because the pauses between symbols are filled with the reflected signal. Evaluation of the ultrasonic signal attenuation in the inner tube space was carried out, and a conclusion was carried out concern the prospects of ultrasonic communication channel.

Nature Tourism in Muar River Valley

Sungai Muar or Muar River is special. Passing through three states of Peninsular Malaysia, it originates in Negeri Sembilan, passes briefly in Malacca, into Johor and ends into the Straits of Malacca. Though laden with history and presently undergoing much socio-economic development, the importance of this river remains inconspicuous, as it is simply known as Sungai Muar. This paper proposes that a geographical official entity be recognized for this river and its surrounding areas as Muar River Valley (MRV) or in Malay, Lembangan Sungai Muar to enhance any future planning and development which would be site-based, thus giving due recognition to the river. Essential data was researched. The geophysical information of MRV is gathered, which forms the first objective of the research. To realistically prove its importance as an official entity, the tourism development was chosen. This research examined previous and potentially new nature tourism research. These are then marked on the map and thus a simple visual appreciation to understand the potential of nature tourism of MRV is easily seen. Hence, a map is produced for existing tourism activities and potential tourism destinations and products in MRV. This forms the second objective. To further enhance, a venture such as nature tourism, that could increase the appreciation to the importance of MRV, a nature tourism product development was done and described, forming the third objective. The exemplary product development is based on a newly recognized oyster species, endemic to MRV named as Crassostrea (Magallana) saidii sp. nov.. All data for the three objectives were obtained through literature search using search engine like Google. Additional methods include interviewing through phone calls, face-to-face, and also Google Meet to obtain information related to land use, drainage and irrigation systems around Bandar Maharani, along with the topography around the extent of Muar District, as basic requirement for the proposal of MRV. Finally, the newly recognized oyster is developed into a tourism product of which the proposed 3 hours package include activities such as observing traditional harvesting of the oysters and tasting of oyster dishes. To complete the nature tourism product development, prototypes of souvenirs are made from shells of the new oysters. For conservation purpose, souvenirs are also made from common species. This recommendation to officiate the designation of MRV would be made to the state government of Johore, through the Muar District Office.

Global Ba/Nb systematics in arc magmas reflect the depths of mineral dehydration in subducted slabs

Abstract The transfer of material from subducting slabs to the overlying mantle is one of the most important processes regulating Earth’s geochemical cycles. A major part of this material cycling involves slab devolatilization and the release of sediment- and slab-derived fluids to the mantle wedge, triggering melting and subsequent arc volcanism. Previous geodynamic, geophysical, and geochemical studies have revealed many important controls on fluid fluxing to the mantle and its manifestations in arc magmas. However, it remains difficult to identify the specific mineral breakdown reactions that control element fluxes from the subducting slab into the overriding mantle. To address this challenge, we combine global arc whole-rock compositional data with geophysical information (e.g., depths to slab) and thermodynamic data. We observe three peaks in Ba/Nb in global arc magma whole-rock compositions corresponding to depths to slab of 60, 120, and &amp;gt;290 km. Using published thermodynamic and geodynamic models of slab evolution, we show that these peaks can be linked to the progressive breakdown of hydrous minerals (e.g., epidote, actinolite, lawsonite) in subducting slabs.